Single-ply membrane roofing incorporates a single-ply polymeric membrane such as EPDM as a water barrier for a roof surface. This can also be used as pond liners as well as other applications. As it is impractical to manufacture polymeric sheeting which can completely cover most roofs, individual sheets are adhered together along lap seams to form a continuous water impervious sheet.
In the past the lap seams have been completely formed at the construction site. This requires that, when necessary, the overlapping edges be cleaned, a primer applied and then an adhesive. Adhesive seam tape is frequently used to form a lap seam. There are a variety of different roofing seam tapes that can be applied. These are generally very tacky. Upon contact they adhere to the overlapped edges of sheeting forming a lap seam.
In order to reduce on-site labor, it is desirable to have the seam tape preapplied to the roofing membrane. Unfortunately, when one preapplies seam tape to the edge of a membrane, it interferes with storing and shipping the sheeting. Typically the sheeting is rolled onto a cylindrical core. Because typical sheeting has uniform thickness, one can roll an indefinite length of material on the core. However, when a seam tape is applied to the edge of the sheeting, the sheeting cannot be simply rolled. The seam edge is twice as thick as the remaining portion of the sheet. Rolling this would form a conical-shaped roll. This interferes with shipping.